(a) Field of the Invention
The present invention relates in general to satellite receive earth stations and, more particularly, to a system for receiving satellite signals from separate and multiple satellites and distributing the signals received from the satellites on a single cable line.
(b) Description of Related Art
Satellite-based communication systems typically beam signals from a terrestrial antenna to a geostationary satellite. The satellite processes and xe2x80x9cdownlinksxe2x80x9d the signals to terrestrial satellite receive antennas located within the satellite""s coverage area or footprint. On-board transponders modulate signals to an assigned carrier frequency and polarity, then send the signals to an on-board antenna for transmission (downlinking) the satellite signals to earth for reception at individual receiver units.
At the individual receiver units at a local earth site, such as a household, a satellite receive antenna, typically comprising a parabolic dish antenna, reflects and concentrates the received satellite signals to a focal point.
Typically, such antennas include a low noise block (LNB) which amplifies, filters and shifts the incoming satellite signal to an intermediate frequency band for coupling to a set-top box or other integrated receiver and detector (IRD) associated with the receiver unit at the local earth site.
At present, there are several different satellite communication services available. For instance, one known direct-to-home digital satellite system now in operation uses an uplink signal modulated onto frequency bands between about 17.2 GHz and about 17.7 GHz. The satellites associated with this system shift the uplink signals to carrier frequencies ranging from approximately 12.2 GHz to approximately 12.7 GHz and transmit these frequency shifted transponder signals back to earth for reception at each of a plurality of individual receiver units in what may be termed a digital television broadcast satellite system or xe2x80x9cDTVxe2x80x9d. Other satellite communication systems are presently available for transmitting digital information to a local earth site for reception and use in a personal computer at the local earth site. For present purposes, such a communication satellite service system is hereinafter identified as a digital personal computer system or xe2x80x9cDPCxe2x80x9d. A DPC satellite communication service system may for instance supply satellite signals at carrier frequencies ranging from approximately 11.7 GHz to approximately 12.2 GHz, which DPC satellite signals are transmitted back to earth for reception at a receiver at the local site.
Accordingly, if a household for instance wishes to subscribe to more than one satellite service, this normally requires the installation of a separate antenna for each satellite service as well as a separate coaxial cable line for distributing the respective satellite service signals to the respective receivers at the local site. A household subscribing to several satellite services thus may require not only an array of satellite receive antennas which is very costly, but also requires the additional expenditures for installing more than the usual single coaxial cable line supplied to one or more rooms in the house.
In a pending application, U.S. Ser. No. 08/544,423 filed Oct. 10, 1995, assigned to the same assignee as herein, there is described a satellite receive antenna capable of simultaneously receiving signals from satellites at different geostationary positions. The aforementioned application Ser. No. 08/544,423 is incorporated herein by reference. This enables one to receive separate multiple satellite communication services signals on a single antenna which therefor eliminates the requirement for a costly antenna array for a household desiring to subscribe to more than one satellite communication service.
However, there is still a need to address the problems in distributing the received separate satellite signals at the outputs of such a dual satellite antenna. In particular, it is desired to distribute the satellite signals from separate multiple satellites on a signal cable line. Further, it is particularly desired to enable a user to access the communication signals from separate multiple satellites simultaneously at for instance different rooms within the household, while only using a single cable to each receiving device.
The present invention relates to a system for distributing satellite communication signals from separate multiple satellites on a single cable line. According to one aspect of the present invention, a dual satellite receiving antenna receives a first broadband signal at a first set of frequency bands corresponding to first satellite service signals, and a second broadband signal at a second set of frequency bands corresponding to second satellite service signals. A frequency converter using frequency division multiplexing receives and converts at least one of the sets of frequency bands to position the converted set of frequency bands adjacent to the other frequency band. A combiner receives the two adjacent frequency bands and distributes them on a single cable line to one or more receivers at the local site for access of the separate multiple satellite communication service signals by the receivers.
According to another aspect of the present invention, a dual mode or two-channel LNB provides both the right-hand polarized and the left-hand polarized signals of a DTV satellite system signal to be provided via separate lines. A frequency converter, utilizing frequency division multiplexing frequency converts the signals from a second satellite system, such as, DPC with each of the separate DTV-left-hand polarization and right-hand polarization signals to provide two adjacent bands of frequency signals, each of which is separately combined in a respective summer unit and distributed on a single coaxial line. A demultiplexer and switch selection circuitry is provided for receiving the two separate lines from the respective summer units and provides a plurality of single cable output lines on which each coupled receiver may simultaneously access any of the received separate satellite signals from the multiple satellites and on a single cable line supplied to the respective receiver.